Sectioned Sacrum, Lateral View

Description

Seen in lateral profile, the lumbosacral junction transitions from the inferior endplate of L5 to the superior base of the sacrum (S1), with the L5 to S1 intervertebral disc interposed anterior to the spinal canal. The sacrum appears as five fused sacral vertebrae forming a triangular wedge, its anterior surface concave and its posterior aspect convex, continuing inferiorly into the coccyx. Superior structures of the vertebral column are included for context, so the cervical lordosis, thoracic kyphosis, and lumbar lordosis read as a continuous sagittal contour. Blue emphasis on the sacrum and coccyx separates the fused segments from the mobile vertebrae at more superior levels. Sagittal alignment at L5 to S1 is a common pain generator and a daily planning problem in spine care, because a small change in sacral slope and lumbar lordosis shifts shear forces across the lumbosacral disc and facet joints. This view also clarifies why anterior spondylolisthesis at L5 to S1 and disc degeneration are mechanically plausible at the junction between a mobile lumbar segment and a rigid sacrum. A key teaching point. The gentle posterior curve of the sacrum, together with its inferior continuation into the coccyx, supports discussions of pelvic incidence and overall spinopelvic balance. Orthopedic and neurosurgical teams use a lateral sacrum and lumbosacral reference image when explaining fusion levels, instrumentation trajectories, or why restoring lordosis matters after deformity correction. It also fits gross anatomy and radiographic anatomy curricula, and works well in textbooks and patient education materials that pair drawn anatomy with lateral radiographs or sagittal CT/MRI concepts. Anatomical accuracy verified by SciePro's Medical Advisory Board.